Waves Types of Waves Mechanical waves require a

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Waves

Waves

Types of Waves • Mechanical waves = require a medium to travel (air, water,

Types of Waves • Mechanical waves = require a medium to travel (air, water, ropes, etc) – Transverse waves – Longitudinal waves • Electromagnetic waves = do NOT require a medium (light, radio waves, microwaves, etc)

Transverse Waves • Cause medium to move perpendicular (90 o) to direction of wave

Transverse Waves • Cause medium to move perpendicular (90 o) to direction of wave

Longitudinal Wave • Cause medium to move parallel to direction of wave • Sound

Longitudinal Wave • Cause medium to move parallel to direction of wave • Sound waves are longitudinal

Comparing Waves

Comparing Waves

Electromagnetic Waves • Do NOT require a medium • Can transmit energy in a

Electromagnetic Waves • Do NOT require a medium • Can transmit energy in a vacuum (empty space) • vibration of charged particles

Crests and Troughs • Crest = Highest point of a sound wave on graph

Crests and Troughs • Crest = Highest point of a sound wave on graph • Trough = Lowest point of a sound wave on graph

Amplitude • Maximum movement of a sound wave from rest.

Amplitude • Maximum movement of a sound wave from rest.

Wavelength (l) • distance between any two consecutive locations on the wave. – crest

Wavelength (l) • distance between any two consecutive locations on the wave. – crest to next crest – trough to next trough – start of wave cycle to next starting point

Crest Trough Rarefaction Horizontal Axis: time in seconds Vertical Axis: molecular movement Crest: higher

Crest Trough Rarefaction Horizontal Axis: time in seconds Vertical Axis: molecular movement Crest: higher pressure Trough: lower pressure Amplitude: height of wave; intensity Compression • • •

Frequency (f ) • Number of complete waves (or cycles) • how many waves

Frequency (f ) • Number of complete waves (or cycles) • how many waves per second • 1 Hertz (Hz) = 1 cycle/second • If ten waves are made per second, then the frequency (f ) = 10 Hz

Frequency • Human hearing 20 Hz – 20, 000 Hz • Subsonic = below

Frequency • Human hearing 20 Hz – 20, 000 Hz • Subsonic = below 20 Hz – Ex: wind, earthquakes • Ultrasonic = above 20, 000 Hz – Ex: Sonar, echolocation, ultrasound

Intensity • Amount of energy of a sound • Measured in Decibels (d. B)

Intensity • Amount of energy of a sound • Measured in Decibels (d. B) • Some sounds with high intensity may be considered noise.

Loud Soft

Loud Soft

Standing Wave • Standing waves appear not to move.

Standing Wave • Standing waves appear not to move.

Let’s compare waves Lower f Higher l Lower l Amplitude same

Let’s compare waves Lower f Higher l Lower l Amplitude same

Let’s compare waves Lower f Higher l Higher Amplitude Higher f Lower l Lower

Let’s compare waves Lower f Higher l Higher Amplitude Higher f Lower l Lower Amplitude

Let’s compare waves Lower f Higher l Lower Amplitude Higher f Lower l Higher

Let’s compare waves Lower f Higher l Lower Amplitude Higher f Lower l Higher Amplitude

Let’s compare waves Higher f Lower l Lower Amplitude Lower f Higher l Higher

Let’s compare waves Higher f Lower l Lower Amplitude Lower f Higher l Higher Amplitude

Which wave has the highest f?

Which wave has the highest f?

Which wave has the highest amplitude?

Which wave has the highest amplitude?

Which wave has the lowest l?

Which wave has the lowest l?

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